Yes and No
When you install a Custom Remote (for a device that is not supported) that remote is actually downloaded it to the Slingbox itself. After that, ANY viewing system (Slingplayer, SlingCatcher, WebSlingPlayer, SlingPlayer Mobile,.,,) will use that remote.
So in that respect the answer is yes.
What you cannot do (unlike on the PC app) is then change the design/image of the remote itself. Whoever designed the iPad app decided the format/layout of the buttons (basically around the outside of the screen) and you are stuck with that design.
So in that respect the answer is no.
I have five Custom Remotes installed on my Slingboxes, two because the devices were not supported and three because I didn't like the default 'skin' image and designed my own, and I have no problem at all with the iPad app.
Thanks for this.
I bought them both, but the remote doesnt work too well on the ipad (as you warned me).
I got a decent workaround though for my device (a Vu+). I can use the Vu+ web app (via dyndns and port forwarding), which has it's own on screen remote, and switch between that app, and the sling app, and it works perfectly.
Now to try and get an increase in outbound speed